The present invention relates to earth retaining walls. More particularly, the present invention relates to connectors used in mechanically stabilized earth retaining walls to join laterally extending soil reinforcement sheets to blocks in the earth retaining wall whereby the tensile loading imposed by backfill on the soil reinforcement sheets is transferred to the earth retaining wall.
Mechanically stabilized earth retaining walls are construction devices used to reinforce earthen slopes, particularly where changes in elevations occur rapidly, for example, development sites with steeply rising embankments. These embankments must be secured, such as by retaining walls, against collapse or failure to protect persons and property from possible injury or damage caused by the slippage or sliding of the earthen slope.
Many designs for earth retaining walls exist today. Wall designs must account for lateral earth and water pressures, the weight of the wall, temperature and shrinkage effects, and earthquake loads. The design type known as mechanically stabilized earth retaining walls employ either metallic or polymeric tensile reinforcements in the soil mass. The tensile reinforcements extend laterally of the wall formed of a plurality of modular facing units, typically precast concrete members, blocks, or panels, stacked together. The tensile reinforcements connect the soil mass to the blocks that define the wall. The blocks create a visual vertical facing for the reinforced soil mass.
The polymeric tensile reinforcements typically used are elongated lattice-like structures often referred to as grids. These are stiff polymeric extrusions defining large sheets. The grids have elongated ribs which connect to transversely aligned bars thereby forming elongated apertures between the ribs. The modular precast concrete members may be in the form of blocks or panels that stack on top of each other to create the vertical facing of the wall.
Various connection methods are used during construction of earth retaining walls to interlock the blocks or panels with the grids. One known type of retaining wall has blocks with bores extending inwardly within the top and bottom surfaces. The bores receive dowels or pins. After a first tier of blocks has been positioned laterally along the length of the wall, the dowels are inserted into the bores of the upper surfaces of the blocks. Edge portions of the grids are placed on the tier of blocks so that each of the dowels extends through a respective one of the apertures. This connects the wall to the grid. The grid extends laterally from the blocks and is covered with back fill. A second tier of blocks is positioned with the upwardly extending dowels fitting within bores of the bottom surfaces of the blocks. The loading of backfill over the grids is distributed at the dowel-to-grid connection points. The strength of the grid-to-wall connection is generated by friction between the upper and lower block surfaces and the grid and by the linkage between the aggregate trapped by the wall and the apertures of the grid. The magnitude of these two contributing factors varies with the workmanship of the wall, normal stresses applied by the weight of the blocks above the connection, and by the quality and size of the aggregate.
Other connection devices are known. For example, my U.S. Pat. No. 5,417,523 describes a connector bar with spaced-apart keys that engage apertures in the grid that extends laterally from the wall. The connector bars are received in channels defined in the upper and lower surfaces of the blocks.
The specifications for earth retaining walls are based upon the strength of the interlocking components and the load created by the backfill. Once the desired wall height and type of ground conditions are known, the number of grids, the vertical spacing between adjacent grids, and lateral positioning of the grids is determined, dependent upon the load capacity of the interlocking components.
Heretofore, construction of such mechanically stabilized earth retaining walls has been limited to large high rise walls. This is due in part the need to have sufficient mass of blocks vertically higher in the wall for securing the soil reinforcement grids to the wall. However, there are numerous small scale projects which could benefit from the use of reinforcement grids and mechanically stabilized earth retaining walls. Low height walls provide insufficient normal loading by the mass of the wall above the grid connections.
Accordingly, there is a need in the art for an improved connector and block for engaging soil reinforcement grids extending laterally from earth retaining walls. It is to such that the present invention is directed.
The present invention meets the need in the art by providing a connector for being received within a channel defined in blocks stacked side by side in tiers to define an earth retaining wall and being engaged to soil reinforcing grids extending through slots from the channels outwardly of the blocks, to transfer tensile loading imposed by backfill on the soil reinforcing grids to the earth retaining wall. The connector comprises an elongate first member that matingly engages an elongate second member. The first member has a plurality of pins spaced-apart along the longitudinal length thereof. Each pin extends in a first direction from a first side of the first member. The second member has a plurality of openings spaced-apart along the longitudinal length thereof for aligning with the pins. The first member and the second member matingly connect by slidingly receiving the aligned pins within the openings while sandwiching therebetween a soil reinforcement grid having open apertures through which the pins extend. The assembled connector is received in a channel defined in blocks that form the wall, for communicating tensile loading on the soil reinforcement grid to the wall.
In another aspect, the present invention provides an earth retaining wall having at least two stacked tiers of blocks placed side by side. Each of the blocks defines a channel extending between opposing sides. The channel defines at least two adjacent bearing surfaces and an opening between the bearing surfaces to a slot extending laterally from the channel to a back side of the block. An elongate connector conforming in cross-sectional shape at least relative to the pair of adjacent bearing surfaces defined in the channel, is received within the channel. The connector comprises an elongate first member that matingly joins an elongate second member. The first member has a plurality of pins spaced-apart along the longitudinal length thereof. Each pin extends in a first direction from a first side of the first member. The second member has a plurality of openings spaced-apart along the longitudinal length thereof for aligning with the pins. A portion of a soil reinforcement grid having a plurality of apertures is sandwiched between the first and the second members and the pins extend through respective apertures. Another portion of the soil reinforcement grid extends from the slot laterally of the blocks. The connector, being engaged to the soil reinforcement grid and received in the channel with the soil reinforcement grid extending through the slot laterally away from the blocks and the extended portion thereof loaded by backfill, mechanically engages the bearing surfaces of the channel to distribute the tensile loading across the wall.
In another aspect, the present invention provides a method of constructing an earth retaining wall, comprising the steps of:
(a) placing at least two stacked tiers of blocks side by side to define a length of a wall, each of the blocks defining a channel extending between opposing sides thereof, the channel defining at least two adjacent bearing surfaces and opening between the bearing surfaces to a slot extending laterally from the channel to a back side of the block;
(b) sandwiching a portion of a soil-reinforcement grid between an elongate first member and an elongate second member that matingly engage together to define a connector, the first member having a plurality of pins spaced-apart along the longitudinal length thereof and each pin extending in a first direction therefrom, the second member having a plurality of openings spaced-apart along the longitudinal length thereof for aligning with the pins, and the soil-reinforcement grid having a plurality of apertures defined therein for being received by the pins while sandwiched between the first and the second members;
(c) sliding the connector with the soil-reinforcement grid along the channel with a portion of the soil-reinforcement grid slidingly received within the slot and extending laterally of the wall; and
(d) covering the portion of the soil-reinforcement grid lateral of the wall with backfill,
whereby the connector, being engaged to the soil-reinforcement grid that is loaded by the backfill, mechanically engages the two bearing surfaces of the channel such that the tensile loading is distributed across the block.
Objects, advantages and features of the present invention will become apparent from a reading of the following detailed description of the invention and claims in view of the appended drawings.